Metal hydride storage apparatus

ABSTRACT

The present invention relates to a miniature metal hydride thermal storage apparatus for the cooling of devices to subambient temperatures, the apparatus composed of at least two chambers containing distinct metal hydrides.

FIELD OF THE INVENTION

[0001] The present invention relates to a miniature metal hydride thermal storage cartridge for the cooling of devices to subambient temperatures, the cartridge composed of two chambers containing two different metal hydrides.

BACKGROUND OF THE INVENTION

[0002] In recent years, the storage of hydrogen as a potential fuel or reactant has become of increasing interest and numerous systems have been described whereby hydrogen can be stored as an interstitial hydride or stoichiometric compound of an appropriate metal, to be released as required, the storage systems being reversible.

[0003] One of these systems utilizes magnesium (Mg) which can form the hydride (MgH₂) from which hydrogen can be driven in gaseous form. A storage system based upon the reversible reaction H₂+Mg+MgH₂ is thus capable of storing hydrogen from a gaseous state upon contact of the hydrogen with the metal and of releasing hydrogen in a gaseous form at a subsequent time and, if desired, at a different place.

[0004] While a number of other materials have also been proposed for the storage of hydrogen in the form of respective hydrides, magnesium has been found to be of interest because of its relatively low cost and light weight which allows for a theoretical capacity of 7.6% by weight of hydrogen (based upon the weight of metal) to be stored and regenerated.

[0005] The storage of hydrogen in the form of magnesium hydride is described, for example, in French Pat. No. 1,529,371 and British Pat. No. 1,171,364. The use of the Mg/MgH₂ system for the reversible storage of hydrogen on an industrial scale, however, poses several practical problems.

[0006] For example, the magnesium should be in the form of a powder so as to obtain the maximum specific surface area for hydrogen absorption and hence the conversion of the Mg to MgH₂ under acceptable conditions.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide a miniature metal hydride thermal storage cartridge for the cooling of devices, e.g., laptop computer chips, to subambient temperatures, the cartridge composed of at least two chambers containing different metal hydrides. The chambers may be connected by a “miniature” valve to control the H₂ flow between the chambers. The metal hydride in each chamber may be formed into a porous structure with multiple hydrogen (H₂) channels.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The above and other objects, features and advantages of the present invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which:

[0009]FIG. 1 displays a metal hydride thermal storage device in conjunction with a set of heat sinks for subambient chip cooling.

[0010]FIG. 2 displays a particular design of the metal hydride thermal storage cartridge for subambient chip cooling.

[0011]FIG. 3 displays a metal hydride thermal storage cartridge inserted into a battery charger for regeneration.

[0012]FIG. 4 displays an alternative hydride structure design.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention relates to a miniature metal hydride thermal storage cartridge for the cooling of laptop computer chips and other mobile electronic consumer devices (e.g., cell phones, mobile cold storage for campers) to subambient temperatures, the cartridge composed of at least two chambers containing different metal hydrides. FIG. 1 shows a design of a miniature metal hydride thermal storage cartridge 10 for cooling of laptop computer chips to subambient temperatures. The cartridge 10 includes two chambers 21 and 22 containing two different metal hydrides, lanthanum nickel metal alloy 23 and magnesium nickel metal alloy 24, as shown in FIG. 2. The two chambers 21 and 22 are connected by an on/off miniature valve 25 that may be activated by the motion of inserting the cartridges 10 or 27 into the main and supplemental heat sinks 28 and 29, as shown in FIG. 1. The chambers and valve form a seamless, cylindrical outer surface, which provides effective contact between the cartridges 10 and 27 and the heat sinks 28 and 29.

[0014] As shown in FIG. 2, prior to utilization of the apparatus of the present invention, all hydrogen should be inside the chamber that has a low-temperature metal hydride, e.g., the magnesium nickel metal alloy chamber 21, and the valve 25 should be closed. Upon inserting the cartridge 10 into the heat sinks 28 and 29, the valve 25 is open, and the hydrogen begins disassociation with the magnesium nickel metal alloy 23 and flows into the lanthanum nickel metal alloy 24 in chamber 22. The two chambers 21 and 22 will reach internal pressure balance when the magnesium nickel metal alloy and lanthanum nickel metal alloy chambers 21 and 22 reach −10° C. and 70° C., respectively. As a result of this process, the cartridge 10 cools the chip 30 to subambient temperatures (e.g., −10° C.), and dissipates the heat (at, e.g., 70° C.) to ambient through the supplemental heat sink 29, as shown in FIG. 1.

[0015] The effective time of use for a particular cartridge depends on both the mass of the metal hydrides inside the cartridge, as well as the cooling requirement. For instance, a chamber of 0.25 inches in diameter and 3 inches long is capable of storing approximately 20 grams of metal hydrides and 0.4 grams of hydrogen. Therefore, the chamber is capable of storing approximately 6,000 joules of thermal energy, assuming the metal hydride has an enthalpy change of hydriding reaction of about 6 kcal/mole-H₂. This is equivalent to 10 watts of subambient cooling for ten minutes. In a preferred embodiment of the present invention, a combination of four cartridges will provide effective cooling for an extended period of time (about 40 minutes) where “super computing performance” is required. In this case, the total amount of hydrogen inside the four cartridges is approximately 1.6 grams.

[0016] The cartridge 10 may be “recharged” by inserting the lanthanum nickel metal alloy end into a hot socket 40, in order to drive all of the hydrogen into the magnesium nickel metal alloy chamber for furture use. This can be done along with recharging the battery 41 in a battery charger 42, as shown in FIG. 3. An added benefit is the cooling of the battery charger 42 by the H₂ disassociation in the lanthanum nickel metal hydride chamber.

[0017] In a further preferred embodiment of the present invention, as shown in FIG. 4, the metal hydride powders are “glued” together and to the chamber inner walls using e.g., silicone. FIG. 4 shows a cross section of chamber 10 containing metal hydrides 43. The H₂ passages 44 may be formed by e.g., mandrels during the “gluing” process. In order to improve the heat conduction of the powder matrix, an effective amount of high conductance metal (e.g., Cu, Si) powders may be mixed with the metal hydride powders before being glued together. Such powders are inert in a hydrogen environment; the powders enhance effective thermal conductivity of the porous structure.

[0018] Thus, a preferred embodiment of the present invention employs the use of two different metal hydrides to achieve subambient cooling of electronic devices, e.g., laptop computers, mobile phones and other consumer electronic equipment. The cartridge-type thermal storage device may be recharged along with batteries. The metal hydrides may be mixed with e.g., copper powder, to improve thermal conductivity. In an alternative hydride bonding design, mandrel-formed H₂ passages in a packed metal hydride powder structure may also achieve the purposes of the present invention.

[0019] While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention. 

What is claimed is:
 1. A miniature metal hydride thermal storage apparatus, which provides for the cooling of devices to subambient temperatures, the apparatus comprising at least two chambers containing distinct metal hydrides.
 2. The apparatus as recited in claim 1, wherein the devices include laptop computers, cellular phones, other mobile electronics and consumer products.
 3. The apparatus as recited in claim 1, wherein the subambient temperatures are no lower than −10° C.
 4. The apparatus as recited in claim 1, wherein the metal hydride is selected from the group consisting of lanthanum nickel metal alloy and magnesium nickel metal alloy.
 5. The apparatus as recited in claim 1, wherein each chamber contains a distinct metal hydride.
 6. The apparatus as recited in claim 1, wherein the metal hydride is combined with high conductance metal powders.
 7. The apparatus as recited in claim 6, wherein said combination promotes heat conduction in the porous structure.
 8. The apparatus as recited in claim 1, wherein the conducting powders are selected from the group consisting of copper, aluminum and silicon powders.
 9. The apparatus as recited in claim 8, wherein hydrogen passages are formed in the metal hydride powder structures by mandrels.
 10. The apparatus as recited in claim 1, further comprising a miniature valve. 